FIELD OF THE INVENTION
This invention relates to an apparatus or machine for mixing and stretching of cheese curd, and more particularly, to a machine for insuring uniform stretching and mixing of Italian pasta-filata cheese for use in the manufacture of pizza and the like.
In recent years, mixing and stretching machines have been developed for mixing cheese curd in contact with heated water and incorporating an elongated motor driven auger for reciving the mixed cheese curd and for stretching the cheese curd during conveying of that curd from the hopper to a vertical accumulator duct at the discharge end of the auger. Such an apparatus forms the subject matter of U.S. Pat. No. 3,713,220 issuing Jan. 30, 1973, to Lester O. Kielsmeier and James G. Leprino. In order to heat the curd during its contact with the water within the hopper initially receiving the cheese curd particles, the apparatus of the referred to patent injects steam directly into the curd water to maintain a given temperature for the water and thus for the curd during mixing and prior to movement through the auger. While the apparatus of the referred to patent constitutes an improvement in the art of manufacturing various types of pasta-filata cheese which are employed in general use in making pizza, there is still great difficulty in developing a good consistent cheese having desired stretchability and uniformity in content. Many of the pizza cheeses which may be purchased in the market today such as mozzarella or provolone cheese have the detrimental characteristics such as bleeding, that is, the fat bleeds out of the cheese, and the stretchability is insufficient such that the cheese does not function right when placed on a pizza Normally, it will not spread evenly and/or has a tendency to burn. It is highly important that a mozarella cheese have the properties of melting uniformly to cover the pizza and to stretch or string on the pizza without burning or turning brown or black. With respect to the obtaining of a mozzarella or provolone cheese having the desired characteristics noted above, the known machines such as those operating under the principles of the referred to patent, have two deficiencies: First, the auger drive speed is excessive and tends to run the cheese through the machine much too fast. The effect of moving the cheese at too rapid a rate defeats the need for the cheese curd to reach a specific temperature and be held at that temperature for a period of time prior to reaching the augers and passing therethrough. Moving the cheese from the water filled hopper where it is subjected to agitation, uniform heating and some stretching at too fast a rate removes the cheese without effecting uniform heating and mixing, and further has a detrimental effect on the utilization of the aguers whose function is not only to remove the cheese from the hot water bath, but to stretch it in accomplishing that end. Thus, the function of the auger is not purely to convey the cheese but to effect its conveyance with sufficient resistance to insure uniform mixing of the cheese and stretching it prior to discharge from the auger.
In the aforementioned patent, back pressure was placed on the cheese curd as it moves through the duct surrounding the auger and leading horizontally from the bottom of the hopper to the vertical cheese accumulator duct or pipe. Back pressure was achieved by the incorporation of a transverse, obliquely inclined plate which narrows the auger duct in a direction away from the hopper and by the utilization of a disc on the auger shaft at its discharge end which limits the cross sectional area of the auger discharge. This results in the narrowing of the pipe or duct carrying the auger, places the restrictor in the vicinity of the auger, limits the back pressure to a small mass of cheese fully within the auger and interferes with stretching and also the removal of manufactured cheese at the termination of a production run such as at the end of the day and in the cleaning of the cheese mixing and stretching machine. Further, the injection of steam or a combination of steam and air under pressure into the hopper to obtain agitation of the water and heating of the same increases the time-temperature requirements for insuring maximum mixing and stretching of the cheese prior to being further stretched and transported by way of the extruder to the vertical accumulator duct.